Everyone has made good suggestions here and it is true that every child is different. I felt myself smiling and nodding as I read.
Some 5 year olds will try anything others you couldn't drag screaming onto the dumbo ride!
One of our four children was just not a "rider". He had been to WDW probably 8 times and still wouldn't go on any of the "good" rides. He wasn't little either, he was almost 10 or 11.
His older NSDB would harass him about this constantly. On a trip a few years ago he finally announced that he was "ready" to ride Space Mountain. I believe this was before FP's. We waited in line forever and he chickened out at the last minute. I had told him that if he went on the ride with me I would let him pick out any t-shirt in the giftshop, something we almost never do.
Needless to say, he was kicking himself in the bee-hind all the way back to the hotel that night. We had planned to spend the last day of that trip at the MK and he did it to us again. We waited in the line and he bailed at the last minute. At this point I thought his brother was going to disown him! About an hour and a half before the park closed he said "Please mom, can I have one more chance?"
Our family split up and he and I went to get in line for the last time. While waiting there was some sort of malfunction and they had to turn on the house lights for a few minutes. He looked around with huge eyes and said, "this is what I'm afraid of!?"
They got things going again and the line started to creep along. I could feel his aprehension building as we got closer and closer to boarding. I couldn't believe that he actually got on that ride! The CM asked him about 4 times if he was okay to ride, and kept looking at me with a worried expression. He barely nodded. He was scared to death but made it through to the end!
When we got off I said "lets hurry so that you can pick out your shirt" I knew that the park was about to close.
When we got to the spot where you kinda veer right to go into the giftshop the ropes were up and the two CM were all the way across the store.
"Hello, I called" "hello, can you help me?" One nice young man came towards us a little and said I am sorry ma'am but the store is closed. I had my credit card in my hand. I asked him if he could make an exception and just pick out a shirt for me, ANY SPACE MOUNTAIN SHIRT in the whole darn store and charge it to me and I'd be on my way. "Sorry" was the reply. "we've already counted out all our drawers and everything. I can't."
OH NO!
I beckoned him a little closer, I was almost in tears! We were leaving in the morning. Quickly, I told him the story of my child who was afraid of rides, who had been to WDW so many times and NEVER ridden, who had just (FINALLY) ridden Space Mountain! He listened, said "wait right here".
A few moments later he came back with a bag which he handed over the rope to my son. In it was a Space Mountain T- shirt ( a cool one with Mickey on it) with plenty of growing room. I reached out my hand with my credit card but he waved me away.
He said: "Just a little PIXIE DUST from one guy that didn't USED to like rides either to another." He smiled at my son, turned and walked away.
That made our trip! We still have the shirt. My son loves ALL the rides now. It took forever, but he finally overcame his fears. Some kids just can't be pushed. Now that he rides, he collects pins of all his favorites.